Materials having special surface properties are widely used in printing, dyeing, bonding, blocking and biological fields etc. For example, polyethylene terephthalate (PET) films having good surface hydrophilicity have good coloring properties, and may be used to print packing materials with various colors and patterns; polymer materials having good surface biological properties may be widely used in fields such as biosensor, medical biological material and biological fast detection.
Generally, materials having different surface properties may be obtained by surface modification. The methods include wet chemical method, chemical etching, corona method, plasma method, high-energy radiation and photochemical method, etc.
UV Initiated Surface Photografting is a photochemical method that immobilizes modification molecules on the surface of materials by covalent bonding with the assistance of UV radiation, so as to achieve the objective of modification. With UV irradiation, the modification molecule is covalently linked to the surface of the materials through surface graft polymerization (polymerization method) or surface coupling (coupling method). The UV coupling method achieves the surface linkage of functional groups and the surface of materials through the bridging action of photosensitive groups, and materials having different surface properties may be obtained by altering the functional groups.
In recent years, the method of polymer surface modification by introducing functional groups through UV coupling has aroused researchers' interests.
J. Biomed. Mater. Res. 1997, 37, 282-290 disclosed a surface modification method on polyurethane by modification molecule in which azidobenzene was used as the photosensitive group and phosphorylcholine as the functional group. The disadvantages of this method include: the nitrene free radical produced by UV radiation of azidobenzene group is excessively active, tending to cause side reaction and result in a decreased efficiency of surface modification; in addition, the substance is extremely reactive and may have post or instant reaction with most compounds, organic solvents and water.
WO 96/31557 disclosed a surface modification method to synthesize a series of compounds using quinone compounds as the photosensitive group. The disadvantages of this method include: quinone groups are comparatively weak in photosensitivity, leading to a comparatively longer UV irradiation time, which is not favorable to fast production and cost saving.
Thus, there is a need in this field for modification molecules containing a photosensitive group that can produce free radicals with desired activity and have comparatively strong photosensitivity, for use in ultraviolet light assisted surface modification method.